Problem: Solve for $z$ : $12 + z = -29$
Solution: Subtract $12$ from both sides: $ \begin{eqnarray} \\ 12 + z &=& -29 \\ \\ {-12} && {-12} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{12 + z} &\hphantom{=}& \hphantom{-29} \\ z &=& -29 {- 12} \\ \end{eqnarray} $ Simplify. $ z = -41$